BOGUS_MIME_VERSION - possible reason is header setting in my email

Question

I`m really new to coding but I try to setup newsletter for my website. I have my own email server on my own server. I send via smtp.

This is header code of my email:

$headers = array(
    'From' => $from,
    'To' => $to,
    'Subject' => $subject,
    'MIME-Version' => 1,
    'Content-type' => 'text/html;charset=iso-8859-1',
    'List-Unsubscribe:  <mailto: [email protected]>,  <https://www.mywebsite.com/unsubscribe.html>'

);

In email I have html code only with linked external *.jpg files.

Thats all.

I run https://www.mail-tester.com/ and in score I get all time BOGUS_MIME_VERSION Other way I will get 10/10.

I think problem is somewere in my &headers.

Can You help me please?

I tried to solve this by my own but after few hours of reading guide I still not know what is wrong with code.